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Neutron Dose Assignment for 

Plutonium Fuel at W.R. Grace

White Paper

National Institute for Occupational Safety and Health

May 1, 2017

Matthew H. Smith

Oak Ridge Associated Universities Team

Reviewed by Thomas P. Tomes 

Division of Compensation Analysis and Support 

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.
White Paper: Neutron Dose Assignment for Plutonium Fuel at W.R. Grace

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

 

INTRODUCTION

Plutonium fuel production at W.R. Grace took place during the period of 1965 to 1972, primarily 

in Buildings 234 and 110. During the period from 1973 to 1987, the facilities were placed in a 

safe standby mode, followed by a decontamination mission that took place between 1987 and 

1994 (Haskins 2007). At this time, the Exposure Matrix for W.R. Grace has limited information 

regarding the assignment of potential neutron dose from this source term during this period. 

Neutron dosimetry data from employees is sporadic – only 15 claims with potential neutron data 

have been identified, and, of these, none contained information from the plutonium fuel 

production period. In addition, no survey data has been located that could be used to develop a 

neutron-to-photon (N:P) ratio (ORAUT 2011). 

PURPOSE

The purpose of this white paper is to determine a reasonable N:P ratio that can be used to assign 

neutron dose for W.R. Grace energy employees who worked in the plutonium fuel fabrication 

process during periods when neutron dose data was not reliable, not available, or not recorded. 

BACKGROUND

The production locations for plutonium fuel fabrication are given in Table 2-1 of the W.R. Grace 

Exposure Matrix (ORAUT 2011). The timeline of production, and decontamination and 

decommissioning (D&D) activities is given above.

MOX Fuel Production Process and Composition

The majority of the plutonium used in the mixed oxide (MOX) fuel production process was 

received from the Hanford site in the form of plutonium nitrate. Smaller amounts of plutonium 

were received from the West Valley and SRS sites.

The MOX fuel production process is summarized in Figure 1 (Booth 1989, p. 118) and described 

in detail in a letter written from R.L. Booth (NFS) to the Department of Energy Richland 

Operations Office in 1989. Further, a summary of the composition of the MOX fuel products is 

given in Table 1 (Booth 1989, p. 119). 

 
White Paper: Neutron Dose Assignment for Plutonium Fuel at W.R. Grace

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its Working Groups or 

Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. 

This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that is 

protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

 

Figure 1. Typical Flow Process of NFS Plutonium Projects (Booth 1989, p. 118). 
White Paper: Neutron Dose Assignment for Plutonium Fuel at W.R. Grace

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions with the ABRWH or its Working Groups or 

Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. 

This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any information that is 

protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

 

Table 1. Plutonium Sources (Booth 1989, p. 119). 
White Paper: Neutron Dose Assignment for Plutonium Fuel at W.R. Grace

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

 

Section 4.3 of the Exposure Matrix indicates that there are no documented neutron exposures at 

W.R. Grace; however, the potential for neutron dose is acknowledged due to the presence of 

highly-enriched uranium and plutonium materials. Due to the low potential for neutron dose, it 

is apparent that the site did not monitor for neutron exposure, especially during the production 

period (ORAUT 2011). 

Since site-specific data for potential neutron dose assignment for this source term is lacking, a 

survey of N:P data associated with plutonium production and fuel fabrication at other sites 

associated with the Energy Employees Occupational Illness Compensation Program Act of 2000 

(EEOICPA) was conducted.

N:P DATA SURVEY FOR PLUTONIUM PRODUCTION AND FUEL FABRICATION

Data for an N:P ratio that could be used for plutonium fuel neutron dose assignment were found 

in several EEOICPA program site profiles or Special Exposure Cohort (SEC) Petition ER 

documents. Plutonium production N:P data is available in the Hanford, Savannah River Site 

(SRS), and Rocky Flats Plant (RFP) external dose site profiles. Data that is more specific to the 

plutonium fuel production process was found in the Nuclear Materials and Equipment 

Corporation (NUMEC) site profile, as well as in data associated with SRS.

Plutonium Production N:P Data

Table 2 provides a summary of the N:P ratios associated with the production and handling of 

plutonium products. 

Table 2. N:P Values for Plutonium Processing Facilities. 

Site N:P Ratio Data Source

Hanford GM= 1.7, GSD = 2.6 (glovebox workers)

GM = 1.1, GSD = 2.3 (non-glovebox) – (For the 

period prior to 1972) 

ORAUT 2010a

SRS GM = 0.91, GSD = 2.84 (HB Line)

GM = 0.36, GSD = 2.52 (FB Line) 

(For the period 1954-1970) 

ORAUT 2005

RFP GM = 0.42, GSD = 3 ( For the period 1977 to 2000) ORAUT 2010b

NUMEC Data

Table 2-3 in Section 2.2.1, and Section 2.2.3.1 of the NUMEC site profile (ORAUT 2017) 

describes the plutonium fuel fabrication process history at that site. These activities may serve as 
White Paper: Neutron Dose Assignment for Plutonium Fuel at W.R. Grace

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

 

a better surrogate for the work that was performed at W.R. Grace (ORAUT 2011). The NUMEC 

work with Fast Flux Test Facility (FFTF) MOX fuel had a similar 20:80 ratio by mass of PuO2 to 

UO2 as seen with the South-West Experimental Fast Oxide Reactor (SEFOR) fuel work at W.R. 

Grace cited in Table 1.

Based on data from worker dosimetry studies performed at NUMEC during work with the FFTF 

fuel, Section 6.5.2.4 recommends an N:P ratio of 0.34 (GSD = 1.71) for general workers and 

1.00 (GSD = 1.49) for glovebox workers (ORAUT 2017).

SRS 321-M Data

N:P data were developed, but not published, based on survey data associated with the Mark 42 

Pu-Al fuel production operations at 321-M at SRS (Brown 2014). The analysis of approximately 

100 paired neutron and gamma survey results yields an N:P ratio of 0.21 ±0.10. A description of 

the process used at 321-M can be found in Section 5.3.4.2.4.2 of the SRS site profile (ORAUT 

2005). 

DISCUSSION

A survey of the available N:P data associated with plutonium processing and plutonium fuel 

fabrication yielded values ranging from 0.34 to 1.7. Because the data from the NUMEC site 

profile are based on worker dosimetry studies, and the work involved plutonium fuel fabrication 

with a composition similar to the product at W.R. Grace, the data from that site are 

recommended for assignment of plutonium fuel neutron dose at W.R. Grace. Specifically, the 

N:P ratio(s) would be defined as lognormal distributions with the following parameters:

• GM = 0.34, GSD = 1.71 (for general workers in Buildings 234 and 110), and

• GM = 1.00, GSD = 1.49 (for glovebox workers in Buildings 234 and 110). 

In order to maintain consistency, assignment of photon and neutron energies should also follow 

the NUMEC guidance from Table 6-8 of ORAUT (2017), which is: 

• Photons: 100%, 30-250 keV, and 

• Neutrons: 100%, 0.1 – 2 MeV. 

Guidance regarding identification of employees who performed plutonium fuel fabrication can 

be found in OCAS-TIB-007 Neutron Exposures at the Savannah River Site. In addition to any 

employee or survivor interview information – or site-provided information - regarding job duties, 

records of plutonium bioassay (if available) would be an indication of external exposure to 

photons and neutrons from a plutonium source term. Further, if a high shallow to deep dose ratio 

(> 2.0) is noted, this could be an indication of glovebox work (OCAS, 2007).
White Paper: Neutron Dose Assignment for Plutonium Fuel at W.R. Grace

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

REFERENCES

Booth, R. L., 1989, letter to R. E. Roesch (U.S. Department of Energy, Richland Operations 

Office), Nuclear Fuel Services, Inc., Erwin, Tennessee, June 7. [SRDB Ref ID: 109631, 

pp. 114-119]

Brown, K. T., 2014, “Documents Requested for Special Exposure Cohort Evaluation,” letter to 

T. D. Taulbee (National Institute for Occupational Safety and Health), Savannah River 

Nuclear Solutions, Savanah River National Laboratory, Aiken, South Carolina, 

January 16. [SRDB Ref ID: 130635]

DCAS (Division of Compensation Analysis and Support), 2011, Best Estimate External Dose 

Reconstruction for Glovebox Workers, DCAS-TIB-0010, Rev. 04, November 28. [SRDB 

Reference ID: 104815]

Haskins, A. A., 2007, Decontamination and Decommissioning of a Uranium Oxide and 

Plutonium Oxide Fuel Fabrication Facility, Transactions of the American Nuclear 

Society, Volume 72, September 18. [SRDB Reference ID: 36182]

OCAS (Office of Compensation Analysis and Support), 2007, Neutron Exposures at the 

Savannah River Site, OCAS-TIB-007, Rev. 00, October 15.

ORAUT (Oak Ridge Associated Universities Team), 2005, Savannah River Site, ORAUTTKBS-0003, Rev. 03, Oak Ridge, Tennessee, April 5.

ORAUT (Oak Ridge Associated Universities Team), 2010a, Hanford Site – Occupational 

External Dose, ORAUT-TKBS-0006-6 Rev. 04, Oak Ridge, Tennessee, January 7.

ORAUT (Oak Ridge Associated Universities Team), 2010b, Rocky Flats Plant – Occupational 

External Dose, ORAUT-TKBS-0011-6, Rev. 02 PC-1, Oak Ridge, Tennessee, 

October 20.

ORAUT (Oak Ridge Associated Universities Team), 2011, An Exposure Matrix for W.R. Grace 

and Company in Erwin, Tennessee, ORAUT-TKBS-0043, Rev. 02, Oak Ridge, 

Tennessee, September 16.

ORAUT (Oak Ridge Associated Universities Team), 2017, Site Profile for Nuclear Materials 

and Equipment Corporation, Apollo and Parks Township, Pennsylvania, ORAUTTKBS-0041, Rev. 04, Oak Ridge, Tennessee, March 7.